# How to turn off a particular bit in a number?

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- Difficulty Level : Easy
- Last Updated : 15 Jul, 2022

Given a number n and a value k, turn off the k’th bit in n. Please note that k = 1 means the rightmost bit.

Examples:

Input: n = 15, k = 1 Output: 14 Input: n = 14, k = 1 Output: 14 The rightmost bit was already off, so no change. Input: n = 15, k = 2 Output: 13 Input: n = 15, k = 3 Output: 11 Input: n = 15, k = 4 Output: 7 Input: n = 15, k >= 5 Output: 15

The idea is to use bitwise <<, & and ~ operators. Using expression “* ~(1 << (k – 1))*“, we get a number which has all bits set, except the k’th bit. If we do bitwise & of this expression with n, we get a number which has all bits same as n except the k’th bit which is 0.

Below is the implementation of above idea.

## C++

`#include <iostream>` `using` `namespace` `std;` ` ` `// Returns a number that has all bits same as n` `// except the k'th bit which is made 0` `int` `turnOffK(` `int` `n, ` `int` `k)` `{` ` ` `// k must be greater than 0` ` ` `if` `(k <= 0) ` `return` `n;` ` ` ` ` `// Do & of n with a number with all set bits except` ` ` `// the k'th bit` ` ` `return` `(n & ~(1 << (k - 1)));` `}` ` ` `// Driver program to test above function` `int` `main()` `{` ` ` `int` `n = 15;` ` ` `int` `k = 4;` ` ` `cout << turnOffK(n, k);` ` ` `return` `0;` `}` |

## Java

`// Java program to turn off a particular bit in a number` `import` `java.io.*;` ` ` `class` `TurnOff ` `{` ` ` `// Function to returns a number that has all bits same as n` ` ` `// except the k'th bit which is made 0` ` ` `static` `int` `turnOffK(` `int` `n, ` `int` `k)` ` ` `{` ` ` `// k must be greater than 0` ` ` `if` `(k <= ` `0` `) ` ` ` `return` `n;` ` ` ` ` `// Do & of n with a number with all set bits except` ` ` `// the k'th bit` ` ` `return` `(n & ~(` `1` `<< (k - ` `1` `)));` ` ` `}` ` ` ` ` `// Driver program` ` ` `public` `static` `void` `main (String[] args) ` ` ` `{` ` ` `int` `n = ` `15` `;` ` ` `int` `k = ` `4` `;` ` ` `System.out.println(turnOffK(n, k));` ` ` `}` `}` `// Contributed by Pramod Kumar` |

## Python3

`# Returns a number that` `# has all bits same as n` `# except the k'th bit` `# which is made 0` ` ` `def` `turnOffK(n,k):` ` ` ` ` `# k must be greater than 0` ` ` `if` `(k <` `=` `0` `): ` ` ` `return` `n` ` ` ` ` `# Do & of n with a number` ` ` `# with all set bits except` ` ` `# the k'th bit` ` ` `return` `(n & ~(` `1` `<< (k ` `-` `1` `)))` ` ` ` ` `# Driver code` `n ` `=` `15` `k ` `=` `4` `print` `(turnOffK(n, k))` ` ` `# This code is contributed` `# by Anant Agarwal.` |

## C#

`// C# program to turn off a ` `// particular bit in a number` `using` `System;` ` ` `class` `GFG` `{` ` ` ` ` `// Function to returns a number ` ` ` `// that has all bits same as n` ` ` `// except the k'th bit which is ` ` ` `// made 0` ` ` `static` `int` `turnOffK(` `int` `n, ` `int` `k)` ` ` `{` ` ` `// k must be greater than 0` ` ` `if` `(k <= 0) ` ` ` `return` `n;` ` ` ` ` `// Do & of n with a number ` ` ` `// with all set bits except` ` ` `// the k'th bit` ` ` `return` `(n & ~ (1 << (k - 1)));` ` ` `}` ` ` ` ` `// Driver Code` ` ` `public` `static` `void` `Main () ` ` ` `{` ` ` `int` `n = 15;` ` ` `int` `k = 4;` ` ` `Console.Write(turnOffK(n, k));` ` ` `}` `}` ` ` `// This code is contributed by Nitin Mittal.` |

## PHP

`<?php` `// PHP program to turn off a ` `// particular bit in a number` ` ` `// Returns a number that has` `// all bits same as n except ` `// the k'th bit which is made 0` `function` `turnOffK(` `$n` `, ` `$k` `)` `{` ` ` ` ` `// k must be greater than 0` ` ` `if` `(` `$k` `<= 0)` ` ` `return` `$n` `;` ` ` ` ` `// Do & of n with a number` ` ` `// with all set bits except` ` ` `// the k'th bit` ` ` `return` `(` `$n` `& ~(1 << (` `$k` `- 1)));` `}` ` ` `// Driver Code` `$n` `= 15;` `$k` `= 4;` `echo` `turnOffK(` `$n` `, ` `$k` `);` ` ` `// This code is contributed by nitin mittal` `?>` |

## Javascript

`<script>` `// Returns a number that has all bits same as n` `// except the k'th bit which is made 0` `function` `turnOffK( n, k){` ` ` `// k must be greater than 0` ` ` `if` `(k <= 0) ` `return` `n;` ` ` ` ` `// Do & of n with a number with all set bits except` ` ` `// the k'th bit` ` ` `return` `(n & ~(1 << (k - 1)));` `}` ` ` `// Driver program to test above function` `let n = 15;` `let k = 4;` `document.write(turnOffK(n, k));` ` ` `// This code is contributed by rohitsingh07052.` `</script>` |

**Output**

7

**Time** **Complexity:** O(1)**Auxiliary Space: **O(1)

**Exercise:** Write a function turnOnK() that turns the k’th bit on.

This article is contributed by **Rahul Jain**. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

My Personal Notes

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